1. Field of the Invention
The present invention relates generally to pipe coupling arrangements and, more particularly, to an arrangement for connecting two adjacent tubular pipe ends in sealing relationship with each other.
2. Description of the Prior Art
Many types of pipe coupling arrangements have been proposed in the art. For example, a coupling sleeve having threaded ends surrounds and threadedly engages cooperating threaded ends of two adjacent pipes. It has also been proposed to enlarge one pipe end to form a bell, and thereupon to jam the other end into the bell to form a joint.
As the use of pipes proliferated, it became desirable to have a better method of joining pipes. One of these methods involved the flanging of a pipe end and the squeezing of the flange between two parts of a fitting or coupling. The threading method, the belling and the flanging methods involved considerable expense and took a considerable amount of time.
According to one proposed version, each pipe end has an enlarged annular threaded cap, and a ring surrounds each pipe end intermediate the latter and the cap. A coupling sleeve having opposite threaded ends threadedly engages the threads of the caps. When the caps were tightened, they constricted the rings.
This type of compression coupling was satisfactory so far as its functioning went. The unsatisfactory part of it was the cost of the compression coupling, i.e., the cost to manufacture it. The caps had to be either machined or forged. Both of these processes were quite slow. Production of the caps was quite limited. Also there were four threading operations, one on each cap and one on each end of the coupling sleeve. These were expensive machining operations.
According to another proposed version, a sleeve surrounds each pipe end and forms clearances with the latter. A short wedge is thereupon jammed into each clearance to wedge the pipe end against the sleeve. However, this type of coupling is not altogether satisfactory in making a tight and reliable clamping seal, because the short wedge does not sealingly engage the entire outer periphery of the respective pipe end. Moreover, since this wedge only engages a short circumferential portion of the respective pipe end, the walls of the pipe ends tend to be stressed and deformed as the wedge is progressively jammed into its clearance. Such deformation of the pipes is undesirable because the resulting constriction prevents free flow through the pipeline.